A Department of Foreign Affairs spokesman confirmed the Consulate-General in Hong Kong had been in contact with an Australian permanent resident, who was under detention.

Mr Ulitzka lists his occupation on social media as the owner of Bentleigh East-based filtered water company, The Freshly Squeezed Water Co.

However, corporate records reveal he ceased to be a director in 2011. He has also been listed as a former director of two de-registered companies: International Water Conservation Systems and Arcacia Pty Ltd.

While some company records show Mr Ulitzka as German born, in others his place of birth is listed as the United States. Social media also shows that Mr Ulitzka was a frequent visitor to the Thai resort town of Pattaya.